most of my friends say you should just use sanding resin when laminating patches or fixing dings with cloth, they say the lam then sanding resin step is just a waste of time so…
I know this sounds like a stupid question but…
is there a reason other than weight/bond issues that you need to lam with laminating resin and then slobber on a thick hotcoat of sanding UV resin just to power sand it all off nice and smooth again?
Is it because you need to squeegee the cloth as dry as possible to maximize its bonding strength?
Never quite totally understood this from the perspective that if you glass it just right in a vacuum bag using a mylar nonstick sheet you can go directly to the finish look with just the lamination, skipping the hot coat and gloss coat process…
So I’m trying to figure out the exact purpose of the three seperate steps when you choose to hand lam other than finished looks.
It just seems weird slobbering on an extra coat when the UV lam kicks so fast in the first place and can leave a much thicker layer of resin on the glass than normal.
Just trying to determine what the UV lam resin is doing with the glass bond that’s different than what the UV sanding resin would do.
After the sanding resin and filler has cured, I like to sand the wax off and then patch with laminating resin and cloth. Cure, sand the edges of my patch, and then hot coat over my patch. Cure and sand. I suppose you could use sanding resin for the cloth at the second stage, but it may not stick as well, if at all. But in theory the wax should rise to the top and that should be that. So, the only option left as I see it, is to try what you think is best and learn from it if it goes wrong.
On larger repairs, using lam resin lets you squeegee the cloth down tighter. Partly to keep the cloth from floating up off the repair area and partly to keep the cloth as thin as possible for a more flush repair. Less of a raised area. The hotcoat on top gives you a bit of a cushion to keep from sanding into the weave and weakening it, except on the edges where you feather it out. You could use sanding resin the same way, but then you could have bonding problems between the lam and hotcoat. You’ll see it when you start sanding it. You get the idea.
On small dings I often just use disposable paint brushes and sanding resin in the cloth with however many layers it takes to level the ding. No hotcoat. Of course there is weave showing all across the sanded finish, but it’s small so it is not very noticeable. Even when you hit it with the finer grits and then polish it.
For me, the plastic cover method is more of an on-the-beach quick fix to limit the rough edges and surface for safety purposes but still needs sanding later to finish it off right. But of course different people do it different ways to serve different purposes.
I’ve never been particular about the composition of patches.
If you get exactly the right amount of material in there, and no bubbles rise to the surface during the cure, then UV lam resin covered with acetate sheet and taped snugly into place will give a very nice glossy finish when the sheet is peeled off. You can re-use the acetate sheet if clean.
Hint for those cursed bubbles that can come up: I slobber just a little UV lam resin into the ding prior to actually patching it. This resin fills all the little shed-holes in the ding and seals the foam. After that, the patch job goes into an already slightly filled area, and there are not hidden voids left to bubble up under the acetate.
If you put in a little too much patch resin, and the acetate is taped so that there is an escape area, then the escaping resin will be paper thin and can be cleaned up by scraping with a chisel, then some wet sandpaper.
Hope this helps. I haven’t bought sanding or finish resin in years. First because I don’t use enough of it for the gallon size not to gel in the can, second because I’m too cheap to buy quarts of it. Lam resin all the way, keep my home-made surfacing agent and a small plastic syringe handy.